fn main() {
    // 这里是 mut 变量，如果不是 mut ，下面的 x = 6 的赋值就会报错
    let mut x = 5;
    println!("The value of x is: {}", x);
    x = 6;
    println!("The value of x is: {}", x);
    let y = x;
    println!("address:{:p} {:p}", &x, &y);

    let s1 = String::from("hello");
    let s2 = s1;

    // println!("{}, world!", s1);
    println!("{}", s2)
}
